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Unix Version 7 - man page for umask (v7 section 2)

UMASK(2)							System Calls Manual							  UMASK(2)

NAME
umask - set file creation mode mask
SYNOPSIS
umask(complmode)
DESCRIPTION
Umask sets a mask used whenever a file is created by creat(2) or mknod(2): the actual mode (see chmod(2)) of the newly-created file is the logical and of the given mode and the complement of the argument. Only the low-order 9 bits of the mask (the protection bits) participate. In other words, the mask shows the bits to be turned off when files are created. The previous value of the mask is returned by the call. The value is initially 0 (no restrictions). The mask is inherited by child pro- cesses.
SEE ALSO
creat(2), mknod(2), chmod(2)
ASSEMBLER
(umask = 60.) sys umask; complmode UMASK(2)